The present disclosure is directed towards systems and methods for treating tissue of a body and more particularly, towards approaches designed to treat a natural joint and conditions involving the knee joint specifically.
A joint is the location at which two or more bones make contact. They are constructed to allow movement and provide mechanical support, and are classified structurally and functionally. Structural classification is determined by how the bones are connected to each other, while functional classification is determined by the degree of movement between the articulating bones. In practice, there is significant overlap between the two types of classifications.
There are three structural classifications of joints, namely fibrous or immovable joints, cartilaginous joints and synovial joints. Fibrous/Immovable bones are connected by dense connective tissue, consisting mainly of collagen. The fibrous joints are further divided into three types: sutures which are found between bones of the skull; syndesmosis which are found between long bones of the body; and gomphosis which is a joint between the root of a tooth and the sockets in the maxilla or mandible.
Cartilaginous bones are connected entirely by cartilage (also known as “synchondroses”). Cartilaginous joints allow more movement between bones than a fibrous joint but less than the highly mobile synovial joint. Synovial joints have a space between the articulating bones for synovial fluid. This classification contains joints that are the most mobile of the three, and includes the knee and shoulder. These are further classified into ball and socket joints, condyloid joints, saddle joints, hinge joints, pivot joints, and gliding joints.
Joints can also be classified functionally, by the degree of mobility they allow. Synarthrosis joints permit little or no mobility. They can be categorized by how the two bones are joined together. That is, synchrondoses are joints where the two bones are connected by a piece of cartilage. Synostoses are where two bones that are initially separated eventually fuse together as a child approaches adulthood. By contrast, amphiarthrosis joints permit slight mobility. The two bone surfaces at the joint are both covered in hyaline cartilage and joined by strands of fibrocartilage. Most amphiarthrosis joints are cartilaginous.
Finally, diarthrosis joints permit a variety of movements (e.g. flexion, adduction, pronation). Only synovial joints are diarthrodial and they can be divided into six classes: 1. ball and socket—such as the shoulder or the hip and femur; 2. Hinge—such as the elbow; 3. Pivot—such as the radius and ulna; 4. condyloidal (or ellipsoidal)—such as the wrist between radius and carps, or knee; 5. Saddle—such as the joint between carpal thumbs and metacarpals; and 6. Gliding—such as between the carpals.
Synovial joints (or diarthroses, or diarthroidal joints) are the most common and most moveable type of joints in the body. As with all other joints in the body, synovial joints achieve movement at the point of contact of the articulating bones. Structural and functional differences distinguish the synovial joints from the two other types of joints in the body, with the main structural difference being the existence of a cavity between the articulating bones and the occupation of a fluid in that cavity which aids movement. The whole of a diarthrosis is contained by a ligamentous sac, the joint capsule or articular capsule. The surfaces of the two bones at the joint are covered in cartilage. The thickness of the cartilage varies with each joint, and sometimes may be of uneven thickness. Articular cartilage is multi-layered. A thin superficial layer provides a smooth surface for the two bones to slide against each other. Of all the layers, it has the highest concentration of collagen and the lowest concentration of proteoglycans, making it very resistant to shear stresses. Deeper than that is an intermediate layer, which is mechanically designed to absorb shocks and distribute the load efficiently. The deepest layer is highly calcified, and anchors the articular cartilage to the bone. In joints where the two surfaces do not fit snugly together, a meniscus or multiple folds of fibro-cartilage within the joint correct the fit, ensuring stability and the optimal distribution of load forces. The synovium is a membrane that covers all the non-cartilaginous surfaces within the joint capsule. It secretes synovial fluid into the joint, which nourishes and lubricates the articular cartilage. The synovium is separated from the capsule by a layer of cellular tissue that contains blood vessels and nerves.
Various maladies can affect the joints, one of which is arthritis. Arthritis is a group of conditions where there is damage caused to the joints of the body. Arthritis is the leading cause of disability in people over the age of 65.
There are many forms of arthritis, each of which has a different cause. Rheumatoid arthritis and psoriatic arthritis are autoimmune diseases in which the body is attacking itself. Septic arthritis is caused by joint infection. Gouty arthritis is caused by deposition of uric acid crystals in the joint that results in subsequent inflammation. The most common form of arthritis, osteoarthritis is also known as degenerative joint disease and occurs following trauma to the joint, following an infection of the joint or simply as a result of aging.
Unfortunately, all arthritides feature pain. Patterns of pain differ among the arthritides and the location. Rheumatoid arthritis is generally worse in the morning; in the early stages, patients often do not have symptoms following their morning shower.
Maladies that can affect the knee joint specifically can be due to misalignment or dislocation. Pain can exist when there is an excess of force contact between the tibia and femur. This can be due to misalignment associated arthritis or anatomical conditions specific to an individual. These problems usually occur toward the medial or lateral sides of the leg and during portions of the gait cycle.
Various muscles and ligaments run along the human leg and certain of these extend across a knee joint (See FIGS. 1A-D). On the lateral side of the knee, a lateral (fibular) collateral ligament extends from the femur to the fibula and an iliotibial band extends from the upper leg to the tibia. The tendon of popliteus also runs between the femur and lower leg and includes a length along the lateral side of the knee as well as a portion which wraps about the back of the knee and connects to the popliteus muscle. The medical (tibial) collateral ligament extends across the knee on a medial side of the joint, as does the arcuate ligament. In the front of the knee, there is the quadriceps tendon above and connected to the kneecap and below and extending from the kneecap is the patellar ligament. Within the knee, there are the anterior cruciate ligament and posterior cruciate ligament. Further, the knee anatomy includes the articular capsule which contains the patella, ligaments, menisci and bursai. Each of such structures can be misaligned or affected by disease causing unnatural gait or individual specific problems.
The knee joint is capable of flexion and extension motions and can undergo slight rotational movement. It is this rotational component that accounts for the frequency of knee injuries. In fact, tissue injury can manifest as swelling about the knee, inability to bear weight or loss of function. Fractures that enter the knee joint often render the joint defective and the once smooth joint surface made irregular. Additionally, fractures resulting in improper limb alignment may contribute to long-term morbidity like arthritis, instability, and functional loss of motion.
The stabilizing ligaments of the knee include the medial collateral ligament (MCL) and lateral collateral ligament (LCL), and are located outside the knee joint proper. The anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) are stabilizer ligaments located within the knee joint. The patellar ligament is located outside the knee joint and functions to provide support for the knee by shielding it, and strengthening the actions of the quadriceps femoris muscle. In particular, the collateral ligaments resist widening of the knee joint. The cruciate ligaments, which are within the knee joint proper resist hyperflexion and hyper extension and also slight rotational movements of the knee. Articular cartilage is bathed by synovial fluid that lubricates the knee joint.
When these ligaments cannot function as intended due to trauma, injury or disease such as arthritis, an individual's knee will not operate properly and pain can result. Conventional treatments have included major surgery where diseased areas of bone are removed or re-shaped or when ligaments are moved or reattached. Such approaches are of course highly invasive and can involve extended periods of recovery and can have limited success.
It has additionally been observed that joints can suffer from specific patterns of disease. For example, lateral osteoarthritis of a joint such as the knee is characterized by a disease pattern tending to be a flexion based disease. As discussed above, the lateral knee has a more complex anatomy than the medial knee and has associated therewith a number of unique neighboring musculoskeletal, vascular and neurological structures, which thereby limit implant real estate. The motion of the lateral knee is also much broader than the medial knee. Such particular patterns of disease can thus necessitate highly specific treatment approaches.
Recently, various approaches to force redistribution in a knee joint have been proposed. In fact, it has been contemplated to insert implants below the patellar tendon, lateral quadriceps-patellar tendon, the biceps femoris tendon, iliotibial band, lateral gastrocnemius, popliteus or fibular collateral ligament to accomplish lateral displacement to realign force vectors and other moment arms loading the knee joint.
Sufficient attention does not appear to have been given in prior joint force redistribution approaches, however, to treatment of the knee joint throughout its full range of motion. Lateral osteoarthritis treatment approaches including those which operate specifically in a manner which unloads a joint in flexion also appear to be lacking. There is a further perceived need for avoiding negative remodeling of the knee ligaments as well as approaches to maintain a desired alignment of an implant and target tissue.
Therefore, what is needed and heretofore lacking in prior attempts to treat joint pain associated with misalignment or dislocation is an implantation method and implant device which addresses full range of joint movement, and which maintains desired structural integrity of anatomy forming the knee joint. There is thus also a need for both passive and active devices for accomplishing desired joint treatments.
The present disclosure addresses these and other needs.